1. Field of the Invention
This invention relates to the art of optometry.
More particularly, this invention relates to corrective lenses for viewing computers and other applications involving close-range work in the upper field of vision.
In a further and more specific aspect, the instant invention concerns a clip-on close range adapter to be worn over a pair of conventional eyeglasses, reading glasses, or bifocals.
2. Description of the Prior Art
Nearly all individuals whose occupations or hobbies involve large amounts of reading or other close work will, at some point in their lives, require corrective lenses to combat blurred vision, headaches, tired eyes, and other symptoms of eyestrain. Severely nearsighted, or myopic, and farsighted, or hyperopic, individuals typically begin to wear such lenses at a relatively young age, and require more and more correction as they get older. It is also common for these individuals to wear bifocal lenses, wherein the upper portion of each lens corrects for long and intermediate range vision, and the lower portion of the lens is suitable for close range, or near-point, vision. According to standard optometric procedure, the prescription for the lower portion of the lens is based on a working distance of 406.4 mm (16 inches).
Even emmetropes, individuals who have "perfect 20/20" vision, may eventually become nearsighted or experience headaches, blurred vision and the like as a result of excessive close work. These individuals typically overcome their difficulties by wearing "reading" glasses--single focus lenses, the prescription for which, again, is based on a working distance of 406.4 mm (16 inches). Such glasses are usually only worn for close work, and are removed while the individual engages in long or intermediate range activities.
The selection of 406.4 mm (16 inches) as the working distance on which the prescriptions for reading glasses and the lower field of bifocal lenses are based is appropriate, since this distance roughly equals the distance from a person's eyes to a desk top or other surface where reading material or paper work is conventionally placed. The location of the close range prescription in the lower field of the bifocal lenses is also appropriate, since most people place their reading material below eye level and look downward while reading.
However, the advent of the personal computer has brought about a new group of vision problems which are not remedied by conventional bifocal lenses or reading glasses. Typically a computer monitor is placed a distance of about 508 mm (20 inches) to 635 mm (25 inches) away from the operator's eyes, and at a height about equal to eye level. Thus, to maintain clear vision, the operator must lean forward in order to get closer to the 406.4 mm (16 inch) working distance for which his or her glasses have been designed. In addition, if the lenses are bifocal, the operator must tip his or head back so that the lower field of the lenses is aligned with the screen. This puts a considerable strain on the operator's neck and back, in addition to causing headaches, tired eyes, and the like.
Similar problems are experienced by piano players, since their sheet music is typically placed 609.6 mm (24 inches) away from their eyes, and by other individuals whose activities require a second close range of vision, involving distances slightly greater than conventional reading distance.
It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.
Accordingly, it is an object of the present invention to provide an optical device suitable for use by a computer operator or piano player.
Another object of the invention is the provision of a pair of lenses having a working distance in the range of 508 mm (20 inches) to 635 mm (25 inches).
And another object of the invention is to provide a pair of close range lenses covering only the upper portion of a person's field of vision.
Still another object of the invention is the provision of a pair of clip-on, close range lenses which can be mounted on a pair of conventional reading glasses or bifocals.
Yet another object of the invention is to provide a pair of lenses for maintaining clear vision at a working distance of 508 mm (20 inches) to 635 mm (25 inches) in an individual's upper field of vision, while maintaining the individual's normal prescription in the lower field of vision.
Yet still another object of the invention is the provision of a pair of pivotable, clip-on lenses which can be flipped down over a user's eyeglasses while the user works on a computer, and flipped up while the user takes a break or looks in the distance.
And a further object of the invention is to provide a pair of clip-on lenses having a focal center horizontally and vertically aligned with the focal center of the user's normal eyeglasses.
And still a further object of the invention is the provision of a pair of glasses including a frame with an upper rim and a pair of close-range lenses extending approximately 27 mm below the upper rim.
And yet a further object of the invention is to provide a pair of corrective lenses for computer users, the prescription for which is determined solely by the age of the user.
And still a further object of the invention is the provision of corrective lenses, according to the foregoing, which are relatively inexpensive to manufacture and comparatively simple and easy to use.